libobs: Clamp audio NaN to 0.0f

Add comparison check so that NaN is caught.
Comparisons with NaN always result in false.
NaNs cause problems later in audio encoder.

Note: may break with -ffast-math compiler flag.

Fixes #4885.

libobs/media-io/audio-io.c

@@ -145,6 +145,7 @@ static inline void clamp_audio_output(struct audio_output *audio, size_t bytes)
 
 			while (mix_data < mix_end) {
 				float val = *mix_data;
+				val = (val == val) ? val : 0.0f;
 				val = (val > 1.0f) ? 1.0f : val;
 				val = (val < -1.0f) ? -1.0f : val;
 				*(mix_data++) = val;